The experiments described here are designed to investigate two related problems regarding the neural architecture of vertebrate retina: 1. the correlation between form and function in retinal ganglion cells, and 2. the functional specificity of retinal amacrine cells as 'local circuit' neurons. Part 1. is designed to test the proposal that the relationship of form and function in ganglion cells is constant (e.g., Maturana et al., 1960). Part 2. is designed to evaluate 3 related models or hypotheses about the function of amacrine cells: 1. Serial synapses among amacrine cells underly the processing of "complex" visual information (Dowling, 1968; Dubin, 1970), and are preferentially associated with ganglion cells having "complex" properties, 2. Within a single stratum of the retina's inner plexiform layer (IPL), synaptic connections occur selectively between specific types of amacrine and ganglion cells, 3. "GABAergic" amacrine cells have a unique distribution of synapses upon directionally sensitive ganglion cells (cf. Wyatt and Daw, 1975). To accomplish these goals, intracellular recording and staining with HRP will be done, first in ganglion cells, then in amacrine cells, and finally in spatially overlapping amacrine/ganglion cell pairs. Ganglion cells will be classified physiologically, stained with HRP, and studied by light microscopy to establish constancy of form and function. Amacrine cells will be studied by the same methods and will be classified with reference to Golgi and also to histochemical studies which localize putative neurotransmitters to specific populations of amacrine cells. Amacrine/ganglion cell pairs will be similarly studied and classified and then their synaptic interconnections analyzed by electron microscopy. EM study of individual, stained cells will form a basis for this final step. These studies will be carried out in in vitro preparations of rabbit and dogfish retinas. Each species is already well-studied and offers special advantages for the proposed research.